they. Of the verbs in these three verses, note that two are in the singular, viz. Leviticus 14:42, "he shall take", and "he shall plaister". Hence the authorities of the second temple interpreted the plural of the owners of the "party-wall", and the singular of the owner of the affected house.
Related Commentaries of Leviticus 14:40
Leviticus 14:40
40 Then the priest shall command that they take away the stones in which the plague is, and they shall cast them into an unclean place without the city: